Principle vs. Principal Examples, Usage, Definition

Principle means “a guiding moral belief” or “a basic truth or theory”:

Out of principle, Rosa refused to take the unfair test on the principles of physics.

Principal means “most important” or “the person in charge of a school”:

The principal reason for the success of Field Elementary School’s principal was her fairness.

When to Use Principle vs. Principal

The word principle is a noun used for “a guiding moral belief or rule” (as in “stand by your principles”). It can also be a noun that means “a basic truth or theory” (as in “the basic principles of chemistry”).

The word principal is an adjective that means “most important” (as in “the principal actor”). It can also be a noun used for “the person in charge of a school” (as in “the principal’s office”). Principal can also be a noun that means “an amount of money borrowed or owed on a loan” or “the amount of an investment on which interest is earned.”

Examples of Principle vs. Principal

He refused to bow, saying it went against his principles.

(In this sentence, “principles” refers to guiding beliefs.)

That argument defies the principles of logic.

(In this sentence, “principles” refers to a basic truth or theory.)

The principal reason Martin went to graduate school was to study algae.

(In this sentence, “principal” indicates the most important.)

East Brookview High School needed a new principal.

(In this sentence, “principal” refers to the person in charge of a school.)

Darren made payments on the principal of his loan.

(In this sentence, “principal” refers to the amount of money owed on a loan.)

How to Remember the Difference

Like many homophones, these words are confusing because they sound alike but their meaning and spelling are different.

Principle is always a noun, so if the word in question is not a noun, you know it must be “principal.”

However, principal can be both a noun and an adjective. When principal is a noun, it refers to “the head of a school” or “an amount of money borrowed or invested.” When it is an adjective, it means “key” or “main.”

And finally, when you want to refer to the head of a school, but can’t remember how that word is spelled, remember the old saying that a “principal” is your “pal” and you’ll have the right word for the job!

Theory Into Practice: Which Is Which?

Is the underlined word correct? See if you can tell.

The principle from Mark Twain Elementary reviewed the new guidelines.

Wrong: This example refers to the person in charge of a school, and should use “principal.”

Lucy is the principle investor in the tech firm.

Wrong: This example refers to the main investor, and should use “principal.”

Dylan’s principal reason for learning to swim was a desire to scuba dive.

Right: This example refers to the main reason for learning to swim and is correct.

There was no principal at Martha’s new progressive school.

Right: This example refers to the person in charge of a school and is correct.

It would violate my principles to conduct scientific research on animal subjects.

Right: This example refers to a guiding moral belief and is correct.

The principal I originally invested has continued to pay dividends during the economic boom.

Right: This example refers to the amount of money on which interest is earned and is correct.